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If the goal is to sell them, it's indeed a good practice to at least mention the environment they were in, especially if from a smoker house, or one in which pets roam freely as some buyers have allergies. Some say that you can't wash these away.
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Joubarc♦Nov 2 '11 at 15:12

15 Answers
15

Ferule +1 And here I thought I was pretty darn smart for figuring this one out... looks like there are a lot of smart people on this site! I use my salad spinner for washing and drying.
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bakoyaroNov 1 '11 at 11:51

I'd never thought of using it for washing - doh!
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Umber FerruleApr 9 '13 at 15:57

Given the collection of some, would a cement mixer do the trick as well? (No, seriously, don't do that, please)
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Joubarc♦Oct 27 '13 at 14:49

How on earth I owned bunnies for a year without even thinking about getting one of these is beyond me... after seeing this answer, I went out and got a BIG (as in, it holds 2+ torn up heads of non-iceberg lettuce) salad spinner for drying Duplos (and Legos, bunny veggies and dinner salads). Best thing ever.
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ImbriumDec 16 '13 at 18:13

LEGO recommend using a mild detergent in water to clean your bricks, or a mild bleach:

We recommend that you clean or wash your LEGO parts only by hand at max. 40°C or 104 degrees (F) Fahrenheit. Higher temperatures may affect the quality of the LEGO parts. You can add a mild detergent to the water, followed by rinsing with clear water. Please don't put your bricks in the washing machine or dishwasher or attempt to dry them in ovens, microwaves or with hair dryers. Any electrical parts, such as cables, motors, battery compartments, can only be wiped off with alcohol. Air-dry parts at room temperature. For disinfecting please use mild bleach.

I don't like reposting my answer from 57, however the questions are sufficiently different that I don't really want to close this one - however it still feels wrong...
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Zhaph - Ben Duguid♦Oct 25 '11 at 21:22

1

I bought a bunch of LEGOs from someone on Craigslist and they stank so I washed them in the bath tub with some bleach. :-)
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Scott Keck-WarrenOct 26 '11 at 12:29

A good quantity of bleach always works for me, even when blocks have been coloured in with felts.
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Umber FerruleApr 9 '13 at 15:50

According to the LEGO Cutomer Service (click "Knowledge Base > How do I sanitize or wash my LEGO elements?"):

We recommend that you clean or wash your LEGO parts only by hand at max. 40°C or 104 degrees (F) Fahrenheit. Higher temperatures may affect the quality of the LEGO parts. You can add a mild detergent to the water, followed by rinsing with clear water. Please don't put your bricks in the washing machine or dishwasher or attempt to dry them in ovens, microwaves or with hair dryers. Any electrical parts, such as cables, motors, battery compartments, can only be wiped off with alcohol. Air-dry parts at room temperature. For disinfecting please use mild bleach.

So the best way to wash all your bricks at once, is to put them into a big bowl, a sink or your bathtub. Add warm water (< 40°C), soap/mild detergent and wash them by hand. Spread the bricks on a towel and let them air dry.

This should be enough to remove dust and loose dirt. For harder grime like stickers or glue-rests there alredy is another question that might also be helpful:

pure alcohol or

glass cleaner

cheap hairspay (spray 2-3 seconds from very close distance and then rub of with a piece of cloth) sometimes also does a good job

Compressed air, commonly used for electronic equipment. Sold in cans at office and electronic stores, used to blow away dust and other small particles away. A paint brush is cheaper but can clear dust from a more localised area. It helps to have a brand new brush that has never been used.

I use compressed air and paint brushes interchangeably when taking pictures of Lego at Minifigure eye-level where dust is more prominent.

I've done this a dozen times the last fortnight, works well. Don't put in tumble dryer after though, as the paint scratches onto other bricks and ruins them. Airing cupboard overnight works well.
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LazlowOct 7 '12 at 16:40

I have polished Lego to restore the shine. Bite marks cannot be removed, so don't bother. Most scratches can either be removed or made much less noticable. Be careful not to be too vigourous in your polishing as the sharp, crisp clean edges of a pristine brick can easily be rounded by an over-zealous polisher. I use a simple buffing wheel w/ a felt (or is it cotton?) wheel,as well as buffing compound.

Increasingly I have done only a light polishing, as I find an overly aggressive approach only results in an unrealistic looking shine that is no longer authentic.

Whatever you do, don't put them in a bath along with small children. It could be that the bathplug gets lifted and then a piece gets sucked into the plug hole. With that piece blocking your ability to put the plug back in the hole, more pieces will be sucked in. Panic will ensue. Small pieces will be swept down the drain, large pieces will continue blocking the hole, water will continue rushing out. Blocking the hole with your hands and fingers won't work. While sweeping the blocking pieces away, new blocking pieces will be sucked in. Those small pieces may be a large number of extremely rare and valuable minifig hands, weapons and utensils. They will not be caught in the S-bend, not with that kind of water velocity.

True story. Just happened tonight.

You could try blocking the hole with a towel or something, to stop the rushing water. That's what I should have done.

heh... hind-sight is 20/20, eh? so sorry that it sounds like you weren't able to retrieve some valuable pieces >< bath tub might work for duplo blocks, but definitely not little pieces!
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ImbriumOct 11 '13 at 8:26

one of those mesh drain covers that minimizes hair and other small objects from going down the drain could possibly help...but still a risk of something going wrong
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Jessica BrownJan 22 '14 at 3:48

Some years ago I picked up some second hand lego and duplo for the kids that was very dirty and grubby and in a general condition that you would not want your kids playing with. The best method I found was to put the items in the bathtub (With the exception of very small pieces that will disappear down the plughole - Put them in a bowl) and spray them with Cif (Jif) lemon bathroom Mouse or similar. Leave for about 10 minutes then Brush using a nylon washing up brush, nail brush or similar. You will be surprised what comes off! Then simply hose off with the showerhead. Then transfer the bricks onto a bathroom towel and dry leave to dry overnight in the airing cupboard, or drape the towel over a radiator and place the bricks on the towel.Biro pen marks can be removed by wiping with methylated spirits and a tissue. Sticky tape residue can be removed with WD40, but then the wd40 need to be remove with a detergent. Hope this helps someone!

I use an ultrasonic cleaner, with either just water or a little washing up liquid. I have also used dishwasher tablets, but this can leave residue on the elements which kinda defeats the purpose of the exercise. I use cold water because the ultrasonic bath heats the water anyway. The benefit of the cleaner is it can clean all nooks and crannies without special tools and it does a very good job. The downside is most ultrasonic cleaners are small so you can't clean large amounts quickly..

For difficult, stubborn dirt and er, stuff, in corners and hard to reach places, I use wooden tooth picks. They're also particularly good for getting dirt from between the letters of the Lego logo on studs. Also, cocktail sticks.

The way I've been washing my Duplo and regular Lego blocks is to fill a clean kitchen sink (or dishpan, storage tub, whatever) with a 50/50ish mixture of hot water (hottest the tap can provide) and white vinegar, then add the blocks. I mix the really hot water and the vinegar together before adding the Legos because that guarantees that the temperature won't be above 104F. If anything is particularly soiled, I use the soft (ie non-scrub-pad) side of a clean sponge to give the blocks a gentle scrubbing as they soak in the warm vinegar water; for anything stuck in difficult-to-clean crevices, I use a baby bottle brush and/or q-tips.

I soak them for a few hours or possibly overnight, then scoop them into a large salad spinner, rinse them thoroughly with warm-to-hot water using the spinner as a colander, spin as much water as I can out and then lay them out on towels to dry (inside, with a box fan blowing across them, flipping them over every few hours until they're totally dry).

Vinegar cleans and disinfects, plus it removes odors (for example, if you buy used Legos online that arrive smelling like cigarette smoke) and it doesn't leave a residue. On top of that, it's 100% kid safe (and pet safe, for any weirdos out there like me who build Lego and/or Duplo creations for small animals :P).

My wife and I have been cleaning up my son's LEGO collection since last week, we clean a small box every noon, since it's a boring task :). We just use a pair of used toothbrushes, pour LEGO parts into a big tub of water mixed with a little dish washing liquid. Then put all them into a washing bag and hang somewhere until they're dry, of course, keep them out of sunlight.